A Texas woman accused of sending ricin-laced letters to President Obama and others in an attempt to frame her husband has reached a plea deal.

Shannon Richardson -- an actress who was pregnant at the time of her arrest in June -- signed a guilty plea, admitting her role in ordering the components to make the ricin and also in mailing the letters, her attorney said today.

In exchange for her plea the federal government has agreed to not sentence her to more than 18 years.

"I think this is an appropriate agreement given the fact that Shannon did not intend to hurt the President or anyone else," her attorney Tonda Curry
said.

There will be a hearing on the plea deal in the next few weeks. However, her sentencing hearing will occur after the conclusion of a pre-sentencing report, which could take three months.

Richardson, 35, initially called the FBI claiming that her husband was the person who had sent a series of letters tainted with small amounts of the toxin ricin to Obama, New York City Mayor Michael Bloomberg and Bloomberg's top gun-control lobbyist in Washington in late May.

But when investigators looked closer, they arrested her June 7 at the couple's home in New Boston, Texas. The actress who played bit roles in movies and on TV shows, including the "Walking Dead," was charged with mailing a threatening communication to the president. She could have faced 10 years in federal prison if found guilty.

"I'm sitting there thinking I don't even know what ricin is," Nathaniel Richardson said. "I wasn't even saying it right at first. I was calling it licin. Really, everything I've learned about it I've learned from [the FBI]."

Shannon Richardson told investigators that she had found small, brown beans with white speckles -- a description matching the key ingredient in ricin, castor beans -- at the couple's home in New Boston. She also told investigators that she had found a sticky note on her husband's desk with addresses for Bloomberg and Obama, the FBI affidavit said.

She failed a polygraph test and investigators found inconsistencies in her story, according to the affidavit.

Finally, the affidavit said, in an interview with authorities June 6, Richardson admitted that she had received syringes and lye -- a caustic chemical used in making ricin -- in the mail; that she had printed the labels for the letters; and that she mailed them.

But she insisted that her husband typed them and "made her" print and send them, the affidavit says.

Richardson was arrested the next day.

Shannon Richardson has appeared on television, including a stint as a zombie on "The Walking Dead" and a role in "The Vampire Diaries."

ABC News' Jenner Smith and Shah Rahmanzadeh and The Associated Press contributed to this report.